High-position filling mining method for lower coal seam based on upper thin coal seam drilling type coal mining

Abstract

The application discloses a high-position filling mining method for lower coal seams based on upper thin coal seam drilling mining, relates to the technical field of filling mining, and is suitable for close distance coal seam groups with upper thin coal seams, mainly relies on upper thin coal seam drilling mining, lower coal seam fully-mechanized mining and high-position filling cooperative operation to realize green and efficient mining of the close distance coal seam groups, and comprises the following steps: judging the high-position filling feasibility of the coal seam group; arranging upper and lower coal seam working faces; first advancing the upper thin coal seam working face and arranging high-position filling flower tubes; advancing the lower coal seam working face and high-position filling; continuously advancing the upper thin coal seam working face and arranging high-position filling flower tubes; and fully mining and fully filling the upper and lower coal seam working faces. The application has the following advantages: the upper and lower coal seams of the coal seam group are completely mined, the coal mining efficiency and resource recovery rate are improved; the upper and lower coal seam goaf is filled at one time, the filling efficiency is high, and there is no gangue emission; and the mine pressure appearance is slowed down and the surface subsidence is inhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of filling mining, in particular to a lower coal seam high-position filling mining method based on upper thin coal seam drilling mining. BACKGROUND

[0002] There are a large number of close distance coal seam groups in China, and a considerable part of them are close distance coal seam groups with thin coal seams in the upper part. There are certain technical limitations in fully recovering the coal resources of such close distance coal seam groups. The mining disturbance of the lower coal seam will lead to an increase in the mining difficulty of the upper thin coal seam or even make it impossible to mine, resulting in a large waste of coal resources. On the other hand, a large number of close distance coal seam groups in China are "three-under" pressure coal, and the mining difficulty is further increased. Therefore, it is urgent to develop a green and efficient coal mining method for close distance coal seam groups, which can realize the simultaneous mining of the upper thin coal seam and the lower coal seam, has a high coal resource recovery rate, a small gangue discharge amount, a small surface subsidence amount, and meets the requirements of safe recovery of "three-under" coal resources. SUMMARY

[0003] In view of the above technical deficiencies, the purpose of the present application is to provide a lower coal seam high-position filling mining method based on upper thin coal seam drilling mining, which can realize the simultaneous and complete mining and filling of the upper and lower coal seams of the close distance coal seam group, avoid the influence of single coal seam mining on another coal seam, improve the coal mining efficiency and resource recovery rate, and at the same time, utilize the caving zone gangue accumulation body and filling material to fill the upper and lower coal seam goaf at one time, so as to improve the filling efficiency, have no gangue discharge, slow down the mine pressure appearance, inhibit the surface subsidence, and realize "three-under" mining.

[0004] To solve the above technical problems, the present application adopts the following technical scheme:

[0005] The present application provides a lower coal seam high-position filling mining method based on upper thin coal seam drilling mining, which is suitable for close distance coal seam groups with thin coal seams in the upper part, mainly relies on upper thin coal seam drilling, lower coal seam fully mechanized mining and high-position filling collaborative operation to realize green and efficient mining of close distance coal seam groups, and includes the following steps:

[0006] Step 1, obtaining the parameter information of the upper and lower coal seams and the roof thereof, and calculating the limit span of the upper and lower coal seam roof, including the upper thin coal seam roof limit span L s and the lower coal seam composite roof limit span L x , and then judging the feasibility of the coal seam group high-position filling;

[0007] Step 2, a drilling roadway is excavated along the upper thin coal seam and a drilling working face is arranged, a spiral drilling coal mining machine is arranged on both sides of the roadway, and a filling material transportation main pipe is arranged along the roof of the roadway; a recovery roadway, an open-off cut and a fully mechanized working face three machines are arranged in the lower coal seam to form a fully mechanized working face of the lower coal seam. The widths L of the working faces of the upper and lower coal seams are equal, and the advancing lengths are equal;

[0008] Step 3, the upper thin coal seam working face is first advanced and a high-position filling flower pipe is arranged, the high-position filling flower pipe is connected with the filling material transportation main pipe; the upper thin coal seam drilling working face is advanced by 0.8L s At this time, the roof of the upper thin coal seam has not collapsed, and the high-position filling flower pipe is arranged to the gob on both sides at a distance of 0.5L x from the end of the drilling roadway and is connected with the filling material transportation main pipe;

[0009] Step 4, the fully mechanized working face of the lower coal seam is advanced by L x , and then the composite roof of the lower coal seam collapses to form a gangue accumulation body with a height of h k ; a high-position filling space with a height of h g is formed between the top of the gangue accumulation body and the uncollapsed roof of the upper thin coal seam; at this time, the filling material with a volume of V is transported to the high-position filling space to consolidate the gangue accumulation body below, and then the high-position filling space is filled;

[0010] Step 5, the upper thin coal seam drilling working face continues to advance by L x , and a high-position filling flower pipe is arranged to the gobs on both sides at a horizontal distance of L x from the last high-position filling flower pipe and is connected with the filling material transportation main pipe;

[0011] Step 6, steps 4 to 5 are repeated until the upper thin coal seam drilling working face and the fully mechanized working face of the lower coal seam advance to the stop line.

[0012] Preferably, in step 1, the specific method for judging the feasibility of high-position filling of the coal seam group is:

[0013] A1, obtaining basic parameters of the upper and lower coal seams of the coal seam group and the roof thereof, including: the coal seam thickness m s of the upper thin coal seam; the roof thickness h s of the upper thin coal seam; the compressive strength σ s of the roof of the upper thin coal seam; the unit weight γ s of the roof of the upper thin coal seam; the coal seam thickness m x of the lower coal seam; the number n of rock layers between the upper and lower coal seams; the thicknesses h1, h2, …, h n of the rock layers between the upper and lower coal seams; the compressive strengths σ1, σ2, …, σ n of the rock layers between the upper and lower coal seams; and the unit weights γ1, γ2, …, γn ;

[0014] A2. Calculate the ultimate span of the upper and lower coal seam roofs, including: the ultimate span L of the upper thin coal seam roof. s and the ultimate span L of the composite roof of the lower coal seam x The ultimate span L of the upper thin coal seam roof s Calculate according to the following formula:

[0015]

[0016] The lower coal seam composite roof is an integral combination of the rock strata between the upper and lower coal seams, with an ultimate span L of the lower coal seam composite roof. x Calculate according to the following formula:

[0017]

[0018] A3. Determine the feasibility of high-level backfilling of coal seams based on the following criteria: thickness of the upper thin coal seam (m). s The thickness of each rock stratum between the upper and lower coal seams must be less than 1.3m, h1, h2, ..., h. n sum The span must be less than 10m, and the ultimate span L of the upper thin coal seam roof. s The ultimate span L of the lower coal seam roof x Requires 0.8L s ≥L x If the coal seam group meets the above criteria, it indicates that high-level filling of the coal seam group is feasible.

[0019] Preferably, in step 4, the filling material is crushed gangue with an aggregate size of less than 1 mm and the auxiliary material is a paste-like filling material of cement and water; based on the ultimate span L of the lower coal seam composite roof. x Determine the mass percentage of each component in the filling material:

[0020] The ultimate span L of the composite roof of the lower coal seam x When the depth is 0-5m, the mass ratio of each component of the filling material adopts the following ratio: 90% gangue, 5% cement, and 5% water.

[0021] The ultimate span L of the composite roof of the lower coal seam x When the depth is 5-10m, the mass ratio of each component of the filling material adopts ratio two, specifically 80% gangue, 10% cement, and 10% water;

[0022] The ultimate span L of the composite roof of the lower coal seam x When the depth is 10-20m, the mass ratio of each component of the filling material adopts ratio 3, specifically 70% gangue, 15% cement, and 15% water;

[0023] The ultimate span L of the composite roof of the lower coal seamx For fill depths greater than 30m, the mass ratio of each component in the filling material is set at 4: 60% gangue, 20% cement, and 20% water.

[0024] Preferably, in step 4, the backfill material volume V is the volume of backfill material required for high-level backfilling after one advance of the lower coal seam fully mechanized mining face, and its determination method is as follows:

[0025] B1. Based on the uniaxial compressive strength σ of the composite roof of the lower coal seam x Determine the value of the fracture expansion coefficient k for the composite roof of the lower coal seam:

[0026] The uniaxial compressive strength σ of the composite roof of the lower coal seam x When the pressure is 0-20 MPa, the coefficient of fragmentation k of the composite roof of the lower coal seam is taken as 1.20;

[0027] The uniaxial compressive strength σ of the composite roof of the lower coal seam x When the pressure is 20-50 MPa, the coefficient of breakage k of the composite roof of the lower coal seam is taken as 1.30;

[0028] The uniaxial compressive strength σ of the composite roof of the lower coal seam x When the pressure is 50-80 MPa, the coefficient of breakage k of the composite roof of the lower coal seam is taken as 1.40;

[0029] The uniaxial compressive strength σ of the composite roof of the lower coal seam x When the pressure is greater than 80 MPa, the coefficient of fracture expansion k of the composite roof of the lower coal seam is taken as 1.45;

[0030] B2. Determine the value of the filling coefficient η for the gangue pile based on the mass ratio of each component of the filling material:

[0031] When using ratio 1, the filling coefficient η of the filling material for the gangue pile is 0.6;

[0032] When using mix ratio 2, the filling coefficient η of the backfill material for the gangue pile is 0.7;

[0033] When using a mix ratio of 3, the filling coefficient η of the backfill material for the gangue pile is 0.8;

[0034] When using a mix ratio of 4, the filling coefficient η of the filling material for the gangue pile is 0.9.

[0035] B3. Calculate the height h of the gangue pile according to the following formula. k :

[0036]

[0037] B4. Calculate the height h of the high-level filling space according to the following formula. g :

[0038]

[0039] B5. Calculate the volume V of the filling material according to the following formula:

[0040] V = L·L x (η·h k +h g ).

[0041] The beneficial effects of this invention are as follows:

[0042] 1. It enables simultaneous backfilling and mining of upper and lower coal seams, avoiding the impact of mining one coal seam on another and improving coal mining efficiency;

[0043] 2. No coal pillars need to be left in the upper and lower coal seam working faces or between working faces. The coal resources of the coal seam group can be completely recovered without coal pillar residue, and the coal resource recovery rate is high.

[0044] 3. Mining the upper thin coal seam does not require the use of hydraulic supports, avoiding the disadvantages of difficult hydraulic support layout and relocation during thin coal seam mining, simplifying the working face production system and reducing working face production costs;

[0045] 4. High-level backfilling utilizes the gangue accumulation in the caving zone to fill the upper and lower coal seam goaf areas in one go. It has high backfilling efficiency, no gangue discharge, effectively solves the problem of gangue discharge and accumulation in mine production, and is conducive to green mining.

[0046] 5. It can effectively alleviate the mining pressure manifestation in the lower coal seam working face, significantly reduce surface subsidence, and realize "three-under" mining. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the stratigraphic relationship between the upper thin coal seam A and the lower coal seam B provided in an embodiment of the present invention;

[0049] Figure 2 This is a side view cross-sectional diagram of the first advance and arrangement of high-level filling pipe in the drilling and mining face of the upper thin coal seam A coal seam.

[0050] Figure 3 yes Figure 2 A top-view cross-sectional structural diagram;

[0051] Figure 4 is a side view profile structure schematic diagram of gangue accumulation body formed by the collapse of composite roof after the first advance of fully mechanized working face of lower coal seam B coal seam;

[0052] Figure 5 is a top view profile structure schematic diagram of Figure 4 ;

[0053] Figure 6 is a side view profile structure schematic diagram of high-position filling material solidified gangue accumulation body and completely filling high-position filling space to form high-position filling material solidified body;

[0054] Figure 7 is a top view profile structure schematic diagram of Figure 6 ;

[0055] Figure 8 is a side view profile structure schematic diagram of upper and lower coal seam working face advance and high-position filling;

[0056] Figure 9 is a top view profile structure schematic diagram of Figure 8 ;

[0057] Wherein: 1-B coal seam; 2-composite roof; 3-A coal seam; 4-A coal seam roof; 5-hydraulic support; 6-high-position filling flower pipe; 7-spiral drill coal mining machine; 8-gangue accumulation body; 9-high-position filling space; 10-high-position filling material solidified body; 11-gangue solidified body solidified by high-position filling material; 12-mining area track transportation main roadway; 13-B coal seam fully mechanized working face air inlet roadway; 14-B coal seam fully mechanized working face air return roadway; 15-drilling roadway; 16-filling material transportation main pipe. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0059] The building, railway pressure area in the range of a certain mine field is about 2.04km 2, a total of about 22.07 million tons of coal resources, of which the 21-1 coal seam in the mining area has a reserve of about 3.05 million tons and the 21-2 coal seam has a reserve of about 7.46 million tons. For convenience of description, the 21-1 coal seam and the 21-2 coal seam are defined as the A coal seam 3 and the B coal seam 1 respectively in the future, the A coal seam and the B coal seam are a close distance coal seam group, the average distance between the coal seams is about 5m, the coal quality of both is high-quality anthracite, and the average inclination of both is about 2°. In order to realize safe, green and efficient recovery of the "three-under" coal resources in the mining area, a high-position filling mining method based on the upper thin coal seam drilling mining is used to recover the "three-under" coal in the A coal seam and the B coal seam close distance coal seam group in the mining area.

[0060] Through field drilling column and laboratory mechanical experiments, it is obtained that the A coal seam is an upper thin coal seam with an average thickness of about 1m and an average buried depth of about 480m. The average thickness of the A coal seam roof 4 is about 7m, the uniaxial compressive strength is about 11.2MPa, and the unit weight is about 25kN·m -3 . The B coal seam is a lower coal seam with an average thickness of about 4m and an average buried depth of about 485m. There are two rock layers between the upper and lower coal seams, which are referred to as rock layer one and rock layer two. The average thickness of the rock layer one is about 3m, the uniaxial compressive strength is about 9.6MPa, and the unit weight is about 24kN·m -3 ; the average thickness of the rock layer two is about 2m, the uniaxial compressive strength is about 7.3MPa, and the unit weight is about 23kN·m -3 . The rock layer one and the rock layer two between the upper and lower coal seams are regarded as a lower coal seam composite roof 2 with a thickness of 5m. The stratigraphic relationship of the A coal seam and the B coal seam is shown in Figure 1 .

[0061] In the embodiment, the thickness of the upper thin coal seam is m s =1m; the thickness of the upper thin coal seam roof is h s =7m; the uniaxial compressive strength of the upper thin coal seam roof is σ s =11.2MPa; the unit weight of the upper thin coal seam roof is γ s =25kN·m -3 ; the thickness of the lower coal seam is m x =4m; the number of rock layers between the upper and lower coal seams is n=2; the thickness of each rock layer between the upper and lower coal seams is h1=3m and h2=2m; the compressive strength of each rock layer between the upper and lower coal seams is σ1=8.2MPa and σ2=7.3MPa; the unit weight of each rock layer between the upper and lower coal seams is γ1=24kN·m -3 and γ2=23kN·m -3 .

[0062] The limit span L s of the upper thin coal seam roof is calculated to be about 25m according to the following formula.

[0063]

[0064] The lower coal seam composite roof limit span L is calculated according to the following formula x about 18m.

[0065]

[0066] In the embodiment, the upper thin coal seam A coal seam has a coal seam thickness m s less than 1.3m, the sum of the rock stratum 1 and the rock stratum 2 thickness h1 and h2 between the upper and lower coal seams is less than 10m, the upper thin coal seam roof limit span L s and the lower coal seam roof limit span L x satisfy 0.8L s ≥L x , so the lower coal seam high filling mining method based on the upper thin coal seam drilling mining can be used to jointly and high filling mine the A and B coal seams in a mining area.

[0067] The B coal seam fully mechanized mining face air inlet roadway 13, the B coal seam fully mechanized mining face air outlet roadway 14, and the open-off cut of the B coal seam are arranged beside the mining area track transportation main roadway 12 of the lower coal seam B coal seam to form a lower coal seam fully mechanized mining face, the working face width L=200m, and the advancing length is 1000m, and the working face roof is supported by the hydraulic support 5.

[0068] A drilling mining roadway 15 is excavated along the center line of the lower coal seam fully mechanized mining face advancing direction below the roof of the upper thin coal seam A coal seam to the upper part of the lower coal seam open-off cut, and a spiral drilling coal machine 7 is arranged on each side of the drilling mining roadway to drill and mine the upper thin coal seam to form an upper thin coal seam drilling mining face, the working face width L=200m, and the advancing length is 1000m. The drilling length of the spiral drilling coal machine is half of the length L of the lower coal seam fully mechanized mining face, 0.5L=100m, and the filling material transportation main pipe 16 is arranged in the drilling mining roadway to transport the filling material.

[0069] The upper thin coal seam A coal seam drilling mining face advances 0.8L s =20m, that is, the spiral drilling coal machine 7 is used to drill and mine the drilling mining face 20m from the end of the drilling mining roadway. At this time, the upper thin coal seam roof has not collapsed, and at a horizontal distance of 0.5L x =9m from the end of the drilling mining roadway, a high filling flower pipe 6 is arranged along the upper thin coal seam roof to the gob on each side and connected with the filling material transportation main pipe 16, as shown in Figure 2 , Figure 3 .

[0070] The lower coal seam B coal seam fully mechanized mining face advances L x =18m, at this time, the B coal seam composite roof reaches the limit span and collapses, and a certain height hk = 6m gangue accumulation body. The gangue accumulation body top and the upper thin seam A seam not caving roof between a certain height h g = 4m space, high filling space 9, as shown in Figure 4 , Figure 5 . After the formation of high filling space, the volume of V = 31680m 3 filling material is transported by filling material transport main pipe to the high filling flower pipe above the goaf. The filling material flows into the high filling space through the high filling flower pipe, first penetrates into the gangue accumulation body to consolidate the gangue, forms the gangue consolidation body 11 consolidated by high filling material, and then fills the high filling space until the high filling space is completely filled, forming the high filling material stone body 10, as shown in Figure 6 , Figure 7 .

[0071] In this embodiment, the filling material is the broken gangue with particle size less than 1mm as aggregate, and the cement and water paste filling material as auxiliary material.

[0072] In this embodiment, according to the lower seam B seam composite roof limit span L x = 18m, the mass ratio of each component of the filling material is determined to be ratio three, specifically 70% of gangue, 15% of cement, and 15% of water. The determination basis of the mass ratio of each component of the filling material is as follows:

[0073] When the lower seam composite roof limit span L x is 0-5m, the mass ratio of each component of the filling material is ratio one, specifically 90% of gangue, 5% of cement, and 5% of water;

[0074] When the lower seam composite roof limit span L x is 5-10m, the mass ratio of each component of the filling material is ratio two, specifically 80% of gangue, 10% of cement, and 10% of water;

[0075] When the lower seam composite roof limit span L x is 10-20m, the mass ratio of each component of the filling material is ratio three, specifically 70% of gangue, 15% of cement, and 15% of water;

[0076] When the lower seam composite roof limit span L x is greater than 30m, the mass ratio of each component of the filling material is ratio four, specifically 60% of gangue, 20% of cement, and 20% of water.

[0077] In this embodiment, the volume of filling material V = 31680m 3 is required for high filling after the lower seam B seam fully mechanized working face advances once, and the determination method of the volume of filling material V is as follows:

[0078] A1, the uniaxial compressive strength σ of the lower coal seam B coal seam composite roof is x 8.1MPa, and the value of the dilatancy coefficient k is determined to be 1.20. The determination basis of the dilatancy coefficient k of the lower coal seam B coal seam composite roof is as follows:

[0079] When the uniaxial compressive strength σ of the lower coal seam composite roof is x 0-20MPa, the dilatancy coefficient k of the lower coal seam composite roof is 1.20;

[0080] When the uniaxial compressive strength σ of the lower coal seam composite roof is x 20-50MPa, the dilatancy coefficient k of the lower coal seam composite roof is 1.30;

[0081] When the uniaxial compressive strength σ of the lower coal seam composite roof is x 50-80MPa, the dilatancy coefficient k of the lower coal seam composite roof is 1.40;

[0082] When the uniaxial compressive strength σ of the lower coal seam composite roof is x greater than 80MPa, the dilatancy coefficient k of the lower coal seam composite roof is 1.45.

[0083] A2, the filling coefficient η of the filling material for the gangue accumulation body is determined to be 0.8 according to the mass proportion of each component of the filling material using the third proportioning. The determination basis of the filling coefficient η of the filling material for the gangue accumulation body is as follows:

[0084] When the mass proportion of each component of the filling material uses the first proportioning, the filling coefficient η of the filling material for the gangue accumulation body is 0.6;

[0085] When the mass proportion of each component of the filling material uses the second proportioning, the filling coefficient η of the filling material for the gangue accumulation body is 0.7;

[0086] When the mass proportion of each component of the filling material uses the third proportioning, the filling coefficient η of the filling material for the gangue accumulation body is 0.8;

[0087] When the mass proportion of each component of the filling material uses the fourth proportioning, the filling coefficient η of the filling material for the gangue accumulation body is 0.9;

[0088] A3, the height h of the gangue accumulation body is calculated according to the following formula k =6m.

[0089]

[0090] A4, the height h of the high-position filling space is calculated according to the following formula g =4m.

[0091]

[0092] A5, the volume of the filling material is calculated according to the following formula: V = 31680 m 3 .

[0093] V = L*L x (η*h k +h g )

[0094] The upper thin seam A coal seam drilling mining working face continues to advance L x = 18 m. At a horizontal distance L x = 18 m from the upper high-level filling flower pipe, a high-level strip filling flower pipe is arranged on both sides of the goaf along the A coal seam roof and connected with the filling material transportation main pipe.

[0095] The upper and lower coal seam working face advancement and high-level filling are repeated, as shown in Figure 8 , Figure 9 , until the upper thin seam A coal seam drilling mining working face and the lower coal seam B coal seam fully mechanized working face are mined to the stop line.

[0096] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for high-level backfilling mining of the lower coal seam based on upper thin coal seam drilling mining, characterized in that, Includes the following steps: Step 1: Obtain parameter information of the upper and lower coal seams and their roofs in the coal seam group, and calculate the ultimate span of the roofs of the upper and lower coal seams, including the ultimate span L of the roof of the upper thin coal seam. s and the ultimate span L of the composite roof of the lower coal seam x This allows for the assessment of the feasibility of high-level filling of coal seams. Step 2: Excavate a drilling and mining roadway along the upper thin coal seam and arrange the drilling and mining face, the spiral drilling coal mining machine, and the main pipeline for transporting backfill materials; arrange the fully mechanized mining face in the lower coal seam. The width L of the upper and lower coal seam working faces is the same, and the advancing length is the same. Step 3: The upper thin coal seam working face is advanced for the first time and a high-level filling pipe is installed. The high-level filling pipe is connected to the main pipeline for transporting filling materials. Step 4: Advance the lower coal seam fully mechanized mining face by L x Subsequently, the lower coal seam composite roof collapsed, forming a section with a height of h. k The gangue deposit; a height of h is formed between the top of the gangue deposit and the uncollapsed roof of the upper thin coal seam. g The high-level filling space; at this time, a filling material with a volume of V is transported to the high-level filling space to consolidate the gangue pile below, and then the high-level filling space is filled to the brim; Step 5: Continue advancing the upper thin coal seam drilling and mining face L x At a horizontal distance L from the previous high-level filling tube x High-level filling pipes are installed in both sides of the goaf and connected to the main pipeline for transporting filling materials. Step 6: Repeat steps 4 to 5 until the upper thin coal seam drilling and mining face and the lower coal seam fully mechanized mining face advance to the stop line; In step 1, the specific method for determining the feasibility of high-level backfilling of coal seams is as follows: A1. Obtain the basic parameters of the upper and lower coal seams and their roof of the coal seam group, including: the thickness (m) of the upper thin coal seam. s The thickness h of the upper thin coal seam roof s σ, the compressive strength of the upper thin coal seam roof s The unit weight γ of the upper thin coal seam roof s The thickness of the lower coal seam is in meters. x The number of rock strata between the upper and lower coal seams, n; the thicknesses of each rock strata between the upper and lower coal seams, h1, h2, ..., h1. n The compressive strengths of the rock strata between the upper and lower coal seams are σ1, σ2, ..., σ. n The unit weights of the rock strata between the upper and lower coal seams are γ1, γ2, ..., γ1. n ; A2. Calculate the ultimate span of the upper and lower coal seam roofs, including: the ultimate span L of the upper thin coal seam roof. s and the ultimate span L of the composite roof of the lower coal seam x The ultimate span L of the upper thin coal seam roof s Calculate according to the following formula: The lower coal seam composite roof is an integral combination of the rock strata between the upper and lower coal seams, with an ultimate span L of the lower coal seam composite roof. x Calculate according to the following formula: A3. Determine the feasibility of high-level backfilling of coal seams based on the following criteria: thickness of the upper thin coal seam (m). s The thickness of each rock stratum between the upper and lower coal seams must be less than 1.3m, h1, h2, ..., h. n sum The span must be less than 10m, and the ultimate span L of the upper thin coal seam roof. s Ultimate span L of the composite roof with the lower coal seam x Requires 0.8L s ≥L x If the coal seam group meets the above criteria, it indicates that high-level filling of the coal seam group is feasible.

2. The method as described in claim 1, characterized in that, In step 3, the upper thin coal seam drilling and mining face is advanced by 0.8L. s 0.5L from the end of the drilling and production roadway x High-level filling pipes are installed in both sides of the goaf and connected to the main pipeline for transporting filling materials.

3. The method as described in claim 1, characterized in that, In step 4, the filling material is crushed gangue with an aggregate size of less than 1 mm and a paste-like filling material of cement and water; based on the ultimate span L of the composite roof of the lower coal seam. x Determine the mass percentage of each component in the filling material: The ultimate span L of the composite roof of the lower coal seam x When the depth is 0-5m, the mass ratio of each component of the filling material adopts the following ratio: 90% gangue, 5% cement, and 5% water. The ultimate span L of the composite roof of the lower coal seam x When the depth is 5-10m, the mass ratio of each component of the filling material adopts ratio two, specifically 80% gangue, 10% cement, and 10% water; The ultimate span L of the composite roof of the lower coal seam x When the depth is 10-20m, the mass ratio of each component of the filling material adopts ratio 3, specifically 70% gangue, 15% cement, and 15% water; The ultimate span L of the composite roof of the lower coal seam x For fill depths greater than 30m, the mass ratio of each component in the filling material is set at 4: 60% gangue, 20% cement, and 20% water.

4. The method as described in claim 3, characterized in that, In step 4, the backfill material volume V is the volume of backfill material required for high-level backfilling after one advance of the fully mechanized mining face in the lower coal seam. Its determination method is as follows: B1. Based on the uniaxial compressive strength σ of the composite roof of the lower coal seam x Determine the value of the fracture expansion coefficient k for the composite roof of the lower coal seam: The uniaxial compressive strength σ of the composite roof of the lower coal seam x When the pressure is 0-20 MPa, the coefficient of fracture expansion k of the composite roof of the lower coal seam is taken as 1.20; The uniaxial compressive strength σ of the composite roof of the lower coal seam x When the pressure is 20-50 MPa, the coefficient of breakage k of the composite roof of the lower coal seam is taken as 1.30; The uniaxial compressive strength σ of the composite roof of the lower coal seam x When the pressure is 50-80 MPa, the coefficient of breakage k of the composite roof of the lower coal seam is taken as 1.40; The uniaxial compressive strength σ of the composite roof of the lower coal seam x When the pressure is greater than 80 MPa, the coefficient of fracture expansion k of the composite roof of the lower coal seam is taken as 1.45; B2. Determine the value of the filling coefficient η for the gangue pile based on the mass ratio of each component of the filling material: When using ratio 1, the filling coefficient η of the filling material for the gangue pile is 0.6; When using mix ratio 2, the filling coefficient η of the backfill material for the gangue pile is 0.7; When using a mix ratio of 3, the filling coefficient η of the backfill material for the gangue pile is 0.8; When using a mix proportion of 4, the filling coefficient η of the backfill material for the gangue pile is 0.9; B3. Calculate the height h of the gangue pile according to the following formula. k : B4. Calculate the height h of the high-level filling space according to the following formula. g : B5. Calculate the volume V of the filling material according to the following formula: V=L·L x (η·h k +h g )。

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